diff --git a/site/ip-addresses.md b/site/ip-addresses.md index 41ca345b..791f19f3 100644 --- a/site/ip-addresses.md +++ b/site/ip-addresses.md @@ -11,7 +11,7 @@ Internet, and you don't have to worry about them clashing. Except, if they actually do clash with some addresses that you'd like the containers to talk to. -Some definitions: +### Some definitions - _IP_ is the Internet Protocol, the fundamental basis of network communication between billions of connected devices. @@ -20,21 +20,30 @@ Some definitions: be between 0 and 255. - Each IP address lives on a _Network_, which is some set of those addresses that all know how talk to each other. The network address - is some prefix of the IP address, like `192.168.48`. To indicate - which part of the address indicates the network, we append a slash + is some prefix of the IP address, like `192.168.48`. To show + which part of the address is the network, we append a slash and then the number of bits in the network prefix, like - `/24`. Another example would be `10.4.2.6/8`, where the network - prefix is the first 8 bits - `10`. Written out in full, the address - of this network is `10.0.0.0/8`. The most common prefix lengths are - 8, 16 and 24, but there is nothing stopping you using a /9 network - or a /26. + `/24`. - A _route_ is an instruction for how to deal with traffic destined for somewhere else - it specifies a Network, and a way to talk to that network. Every device using IP has a table of routes, so for any destination address it looks up that table, finds the right route, and sends it in the direction indicated. -Quick example: this is the route table for a container that I just started: +### Examples + +In the IP address `10.4.2.6/8`, the network prefix is the first 8 bits +- `10`. Written out in full, that network is `10.0.0.0/8`. + +The most common prefix lengths are 8, 16 and 24, but there is nothing +stopping you using a /9 network or a /26. E.g. `6.250.3.1/9` is on the +`6.128.0.0/9` network. + +Several websites offer calculators to decode this kind of address; for +example [IP Address Guide](http://www.ipaddressguide.com/cidr). + +Here is an example route table for a container attached to the Weave +network: ```` # ip route show @@ -57,9 +66,11 @@ Net will take care of routing the traffic. To talk an external server at address `74.125.133.128`, it looks in its routing table, doesn't find a match, so uses the default rule. +### Configuring Weave + The default configurations for both weave Net and Docker use [Private Networks](https://en.wikipedia.org/wiki/Private_network), whose -addresses are never used on the public internet, so that reduces the +addresses are never found on the public internet, so that reduces the chances of overlap. But it could be that you or your hosting provider are using some of these private addresses in the same range, which would cause a clash. @@ -75,14 +86,18 @@ You must pick another range and set it on all hosts. As the message says, the default that weave Net would like to use is `10.32.0.0/12` - a 12-bit prefix so all addresses starting with the bit -pattern 000010100010, or in decimal everything from 10.32 through -10.47. But the user's host already has a route for `10.0.0.0/8`, +pattern 000010100010, or in decimal everything from 10.32.0.0 through +10.47.255.255. But the user's host already has a route for `10.0.0.0/8`, which overlaps, because the first 8 bits are the same. If we went ahead and used the default network, then for an address like `10.32.5.6` the kernel would never be sure whether this meant the weave Net network of `10.32.0.0/12` or the hosting network of -10.0.0.0/8. +`10.0.0.0/8`. -If you're in this situation, the best option is, as the message says, -to pick a different range. In this example, a different private range -such as `172.30/16` would work. +If you're sure the addresses you want are not really in use, then +explicitly setting the range with `--ipalloc-range` in the +command-line arguments to `weave launch` on all hosts will force Weave +Net to use that range, even though it overlaps. Otherwise, you can +pick a different range, preferrably another subset of the [Private +Networks](https://en.wikipedia.org/wiki/Private_network). For example +172.30.0.0/16. diff --git a/site/ipam.md b/site/ipam.md index 30901fbf..74288e93 100644 --- a/site/ipam.md +++ b/site/ipam.md @@ -109,7 +109,8 @@ The range parameter is written in [CIDR notation](http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing) - in this example "/16" means the first 16 bits of the address form the network address and the allocator is to allocate container addresses -that all start 10.2. [More information on IP addresses and routes](ip-addresses.html) +that all start 10.2. We have [a page with more information on IP +addresses and routes](ip-addresses.html). Weave shares the IP address range across all peers, dynamically according to their needs. If a group of peers becomes isolated from